1. Field of the Invention
This invention relates to fertilizing materials for alkaline and acid soils and to a method of preparing and using such materials.
2. Description of Related Art
Highly acidic fertilizers for calcerous (alkaline) soils made from iron and copper refining slags are already well-known. However, there has been a continuing need to develop fertilizers, and processes for making same, which have increased equivalent acidity per unit weight and which will release their acidity to the soil over an extended period of time. In addition, there is a continuing need for fertilizers useful for application to both alkaline and acid soils.
U.S. Pat. No. 3,359,091 teaches the treatment of mine tailings containing substantial amounts of iron sulfides with 25% by weight of concentrated sulfuric acid followed by heating above 200.degree. C. and hardening by treatment with ammonia.
U.S. Pat. No. 3,860,409 teaches the treatment of pulverized waste copper slag with concentrated sulfuric acid, addition of water, and allowing the product to stand until dry. The product is a dry granular gel composed of 80-85% of water soluble, partially hydrated, but mostly anhydrous, metallic sulfate salts in combination with metasilicic acid-absorbed sulfuric acid, approximately 15-20% of sulfuric acid insoluble iron and aluminum silicates, and approximately 1-2% of elemental sulfur.
The acidic fertilizers of the prior art are characterized by relatively low concentrations of reactive iron.